1. Field of the Invention
The present invention relates to a compressor and a manufacturing method thereof.
2. Description of Related Art
For instance, Japanese Unexamined Patent Publication No. 2008-215284A teaches a compressor, which includes a compressing device and an electric motor device received in a casing. The compressing device is configured to compress refrigerant, and the electric motor device is configured to drive the compressing device. The compressing device and the electric motor device are coupled with each other through a drive shaft. A bearing device, which rotatably supports the drive shaft, is fixed in the casing.
The casing includes a cylindrical tubular body portion and upper and lower cover portions. The upper and lower cover portions are fixed to upper and lower end parts, respectively, of the cylindrical tubular body portion by welding.
The compressor of Japanese Unexamined Patent. Publication. No. 2008-215284A is assembled through the following assembling procedure. That is, the compressing device, the electric motor device, the drive shaft and the bearing device are assembled into the cylindrical tubular body portion of the casing. Thereafter, the upper and lower cover portions are fixed to the upper and lower end parts, respectively, of the cylindrical tubular body portion by welding.
The inventors of the present invention have proposed to provide a required sealing performance of the casing by executing all-around welding (360 degree welding) to weld between the cylindrical tubular body portion and each of the upper and lower cover portions along the entire circumference of the cylindrical tubular portion. Furthermore, in order to limit a seal failure at a welding start point where the weld penetration is unstable, the inventors of the present invention have also proposed to execute the welding through an angular range of 360 degrees+α. Here, “α” denotes an additional angle. In this way, a welding end point is located beyond the welding start point, so that a welding bead at the welding start point and a welding bead at the welding end point are overlapped with each other.
However, when the welding beads are overlapped with each other to form an overlapped portion, the amount of heat input at the overlapped portion becomes large, and thereby a welding distortion becomes large at the overlapped portion. Therefore, the inner diameter of the casing at the overlapped portion becomes smaller than the inner diameter of the casing at the other circumferential portion (see FIG. 5A described below).
Therefore, the location of the bearing device, which is assembled into the casing, may be deviated from its appropriate location (designated location), and thereby the location of the drive shaft may be also deviated from its appropriate location (designated location). Therefore, an operational reliability of the compressor is disadvantageously deteriorated.